Fuel injection system

ABSTRACT

A fuel injection system for an internal combustion engine is disclosed. The system includes a fuel supply tank, a fuel supply system between the tank and the engine, a fuel return system for returning fuel to the tank from the engine and a fuel flow governor controlling fuel flow in the supply system in response to fuel pressure in the return system. The supply system includes a fuel injection pump which normally supplies quantities of fuel to fuel injectors in excess of the fuel injected into the engine. The flow governor includes a fuel control valve for modulating the flow of fuel to the injectors in response to the level of fuel pressure in the fuel return system to prevent oversupply of fuel to the engine.

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tte tetes Patent 1151 31,63,629

Moon Feb. 1, 1972 [54] FUEL INJECTION SYSTEM 1,059,239 10/1954 Germany ..l23/l39 [72] inventor: Charles L. Moon, Brecksville, Ohio OTHER PUBLICATIONS [73] Assignee: glllrige Motor Corporation, Cleveland, 1[.{ydmulicpkmdbook,n 1953 pages 1 &27

- Primary Examiner-Laurence M. Goodridge 19 [22] Oct 2 69 Assistant Examiner-Ronald B. Cox [21] Appl. No.: 863,310 At!0meyWatts, Hoffmann, Fisher & Heinke 52 us. c1. ..123/l39.6,123/139 AZ, 123/140 A, [5 ABSTRACT 123/140 R A fuel injection system for an internal combustion engine is [51] Int. Cl ..........F02m 39/00, F02d 1/04 disclosed. The system includes afuel supply tank, a fuel supply [58] Field of Search ..123/139, 140, 140 A, 139 A2, system between the tank and the engine, a fuel return system l23/l39.6; 137/87 for returning fuel to the tank from the engine and a fuel flow governor controlling fuel flow in the supply system in response [56] Referen e Cited to fuel pressure in the return system.

UNITED STATES PATENTS The supply system includes a fuel injection pump which normally supplies quantities of fuel to fuel injectors in excess of 2,347,363 4/1944 Palumbo ..123/139.6 the fuel injected into the engine. The flow governor includes 3 2,446,497 8/1948 Thomas 1 39 fuel control valve for modulating the flow of fuel to the injec- 2,536,556 l/l95l Lawrence ..l23/l39 tors in response to the level of fuel pressure in the fuel return 3,231,003 1/1966 Richcreek 123/ 1 39.6 system to prevent oversupply of fuel to the engine.

FOREIGN PATENTS OR APPLICATIONS 9 Claims, 3 Drawing Figures FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fuel injection systems for internal combustion engines and more particularly relates to fuel injection systems having a fuel injection pump which supplies fuel to fuel injectors in excess of the amount of fuel injected into the engine for combustion.

2. The Prior Art Fuel injection systems for internal combustion engines employing fuel injection pumps which supply fuel to injectors in quantities which exceed the quantity of fuel injected into the engine have been constructed in the past. Such systems insured that adequate fuel charges were injected into the engine. The excess fuel also provided cooling and/or lubrication for the injectors. In some cases, the excess fuel was a means for controlling the metered quantity of fuel for injection.

The injectors of such systems were normally piston-cylinder devices operated from the engine to deliver predetermined charges of fuel to the combustion chambers. in order to avoid the injection of excessively large fuel charges into the engine, systems of the type referred to were provided with injectors designed to discharge excess fuel supplied to them from the injection pump. Excess fuel return passages communicated the fuel discharged from the injectors to the fuel supply tank.

When the fuel return passages were blocked, these fuel injection systems overfueled the engines. This was particularly true when such fuel injection systems were used in over-theroad truck tractor units. It was common practice for drivers or operators of trucks to block the fuel return lines in order to increase the horsepower output of the engine by increasing the fuel charges injected into the combustion chambers. This was generally accomplished by clamping, or kinking a fuel return line, or by inserting restrictions into a fuel return line. This tampering increases the pressure in the fuel return system to a level at which the injectors could not exhaust the excess fuel supplied to them. The high-pressure excess fuel was then forced into the combustion chambers along with the requisite charge resulting in overfueling of the engine.

Overfueling engines beyond their design point resulted in: l decreased engine life; (2) decreased fuel economy; (3) excessive exhaust smoke; and (4) overheating the engine as a result of increasing the heat load on the engine coolant system beyond its design limitations. Hence, although impeding the fuel return flow from the injectors to the fuel tank resulted in improved performance of a given engine over the short term, these unauthorized modifications had such serious adverse effects on engines over the long term that the prior art attempted to discover a system which would thwart would-be tamperers.

One proposed system included a fuel shutoff valve located in a fuel line between the fuel supply tank and an injection pump. The valve terminated the flow of fuel from the fuel tank to the injection pump in response to pressure increases in the fuel return line. Thus, if the return line were blocked, the flow of fuel to the engine was terminated, or substantially terminated, thereby disabling the vehicle.

This prevented overfueling but had the disadvantage of disabling the truck whenever the return line was tampered with.

Since blocking fuel return lines is a practice which is not condoned by those ultimately responsible for the engines, drivers or operators of trucks generally attempted to block the return lines while on the road, or someplace where they were not likely to be discovered tampering with the fuel injection systems. Use of the prior art devices gave rise to the likelihood of tampered-with vehicles being disabled remote from servicing facilities. This was undesirable for a number of reasons which should be apparent.

The prior art devices generally included pressure responsive valves which terminated the flow of fuel to the injection pump when return fuel pressure increased above a given level. Since most injection pumps are lubricated and cooled at least in part by the fuel flowing through them, terminating the fuel flow to the injection pumps could damage them.

Furthermore, these proposed devices were constructed in such a way that the fuel return line was easily blocked between the valve and the injectors. When the return line was blocked in such a location the valve was disabled and fuel oversupply was accomplished. in short, the prior art proposals were themselves subject to tampering.

SUMMARY OF THE lNVENTlON The present invention provides a new, and improved fuel injection system for an internal combustion engine including a fuel supply tank, a fuel supply system between the tank and the engine, a fuel return system, and a fuel flow governor for modulating fuel flow in the fuel supply system in response to fuel return system pressure. The fuel supply system includes a fuel injection pump, at least one fuel injector and fuel lines communicating the tank with the pump and the injectors. The pump supplies excess fuel to the injectors to insure the injection of adequate fuel charges. The excess fuel is returned to the fuel tank through the fuel return system.

The fuel governor modulates the flow of fuel to the injectors in response to fuel pressure in the return system and includes a valve having a movable valve member which variably restricts flow in the fuel supply system. The valve communicates with an excess fuel return passage by way of a pressure-transmitting passage, or pressure reaction conduit, which communicates the static pressure of the fuel in the return passage to a pressure reaction surface on the valve member. When the pressure in the return passage increases, resulting pressure forces are exerted on the valve member. The valve member is moved to restrict the flow of fuel to the injectors in relation to the pressure level in the return passage. In this manner, oversupply of fuel to the engine is avoided and yet injected fuel charges are maintained within design limits to permit continued operation of the vehicle.

Since the fuel flow control valve operates in response to the static pressure of fuel in the return passage, the new fuel governor system is disabled only if the fuel return passage is blocked and the pressure-transmitting passage between the valve and the return passage is completely blocked. if the pressure-transmitting passage is not totally blocked, the static pressure of the fuel in the return passage is gradually communicated to the valve resulting in modulation of the fuel supply.

in a preferred embodiment, the fuel control valve is located between the injection pump and the injectors and controls the flow of fuel discharged from the injection pump. Preferably, the excess fuel valve is integral with the injection pump to minimize the number of external conduits and possibilities for tampering. Accordingly, when the new fuel control valve impedes the flow fuel to the injectors, the injection pump is continuously supplied with fuel. This insures against overheating or insufficient lubrication of the fuel injection pump.

in a preferred embodiment, the pressure reaction conduit between the fuel return passage and the fuel control valve communicates with a fuel return rail or manifold. Thus, it is extremely difiicult for operators of vehicles to restrict the return flow of fuel to the tank in such a way as to render the new fuel governor system inoperative since the rail itself would have to be blocked between some of the fuel injectors and the pressure reaction conduit.

Blocking the fuel return passages in the vicinity of the fuel return rail is both difficult and easily discoverable and therefore not resorted to.

An object of the present invention is the provision of a new and improved fuel control system for governing the flow of fuel to injectors of an internal combustion engine in response to the pressure of the fuel in a fuel return passage and which is relatively tamperproof, insures adequate lubrication and cooling of a fuel injection pump of the system, and permits continued operation of a vehicle when the injection system has been tampered with.

BRIEF DESCRIPTION OF THE DRAWINGS H6. 1 is a schematic illustration of a fuel injection system embodying the present invention;

P10. 2 is a cross-sectional view of a fuel flow control valve forming a part of the system of FIG. I and shown on a scale which is larger than the scale of HQ. 1; and,

FIG. 3 is a cross-sectional view of a modified fuel-flow-controlling valve constructed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel injection system for an internal combustion engine 11 (broken lines) is illustrated in FIG. 1. The system 10 includes a fuel tank 12, a fuel supply and delivery system 13, a fuel return system 14, and a fuel flow governor 15. The system 13 withdraws fuel from the tank 12 and delivers metered quantities of the fuel to combustion chambers of the engine 11. The system 13 is constructed to provide a flow rate of fuel to the engine 11 which is in excess of metered quantities of fuel injected into the combustion chambers. The excess fuel is returned to the tank 12 through the fuel return system 14. The fuel flow governor 15 modulates the flow of fuel to the engine in response to fluid pressure in the return passage to avoid oversupply of fuel.

The engine 11 may be of any suitable construction, and is illustrated as a V-block eight-cylinder diesel of a commercially available type. Accordingly, the engine is neither shown nor described in detail. The fuel tank 12 is likewise of conventional construction and is therefore illustrated schematically.

The fuel supply and delivery system 13 includes a fuel injection pump assembly 30, fuel injectors 32 and fuel conduits communicating the tank 12 with the injection pump and injectors. In the illustrated fuel supply system, a fuel filter 34 is connected between the tank 12 and the fuel injection pump in a conduit 35.

The injection pump assembly 30 includes a fuel transfer pump 40 and a metering device 41. The transfer pump and metering are conventional and are not described or illustrated in detail. A metered volume flow rate of fuel is discharged from the pump assembly 30 and communicated with the injectors 32 through a flow control valve 44 (described in greater detail presently), a conventional fuel shutoff valve 46, a fuel delivery conduit 50, a delivery manifold or rail 52 and individual injector delivery lines 54.

The fuel injection pump 30 normally delivers a greater quantity of fuel to each injector than is injected into the associated combustion chamber. This insures an adequate fuel charge being injected into each combustion chamber by each injector.

The injectors 32 are preferably of the piston-cylinder type in which the piston moves through its stroke to inject a predetermined fuel charge into an associated combustion chamber, during a compression stroke of the piston of the combustion chamber. The injectors 32 are constructed so that the excess fuel delivered to them is exhausted to the fuel return system 14. Injectors of the type referred to are known and accordingly a detailed description of their construction and operation is unnecessary.

The fuel return system 14 includes individual injector return conduits 60, a fuel return manifold, or rail, 61 and a fuel return line 62 communicating the rail 61 to the fuel tank through a suitable connector 63.

The injectors are positive displacement devices and if the return system is blocked the fuel pressure in the return system tends to increase substantially due to the substantially incompressible nature of the fuel. In the absence of any structure for controlling fuel flow in the injection system, the high-pressure fuel in the return line will prevent excess fuel from exhausting from the injectors and the injectors are forced to deliver the excess fuel supplied to them into the combustion chamber. This results in overfueling the engine and is likely to damage the engine as has been noted.

The fuel flow governor 15 modulates the flow of fuel from the injection pump assembly 30 to the injectors 32 in relation to the pressure level of the fuel in the return rail 61. Thus, oversupply of fuel to combustion chambers is avoided even when the fuel return system 14 is blocked. The flow governor includes the valve 44 and a pressure reaction or pressuretransmitting conduit 70 communicating the valve 44 with the return rail 61. The valve 44 includes a housing 73 which is preferably integral with the injection pump assembly 30. The housing 73 defines a fuel flow passage 74 extending through the housing for communicating the discharge of the fuel injection pump 30 to the injectors 32 through the fuel shutoff valve 46 and the passages 50, 52 and 54. A valve member 75 is supported in the housing 73 and is movable to variably restrict flow through the passage 74.

The valve member 75 includes a cylindrical valve body 76 and a pressure reaction piston 78. The valve body 76 is snugly supported in a smooth bore 80 which extends through the housing 73 and intersects the passage 74. The pressure reaction piston 78 is disposed in a cylinder bore 82 at one end of the bore 80. The cylinder bore 82 extends through a side of the housing 73 and is closed by a suitable plug 84 threaded into the end of the cylinder bore.

The valve member 75 is normally positioned to provide minimum restriction of fuel flow through the passage 74 (H6. 2). The valve member 75 is biased to the minimum restriction position by a helical compression spring 86 supported between an end 88 of the bore 80 and an adjacent end 90 of the valve member. The spring 86 urges the valve member toward the right, as seen in H0. 2. A limit position of the valve member is reached when the piston 78 engages a stop 92 on the plug 84. ln this position, a spool 94 formed on the valve body 76 extends across the passage 74 enabling a maximum fuel flow through the passage.

The valve member is movable away from the full flow position in response to fuel pressure in the return system 14. A pressure reaction chamber 96 is formed between the piston 78, the plug 84, and the surrounding wall of the cylinder bore 82. The pressure reaction conduit 70 communicates the fuel pressure in the return rail 61 to the chamber 96. The return fuel pressure creates a pressure force which acts on the piston 78 tending to shift the valve member towards the left (FIG. 2) against the spring 86.

When the return fuel. pressure reaches a predetermined level, the pressure force on the valve overcomes the spring force and moves the valve member until the pressure force and spring force are balanced. The fuel flow through the passage 74 is restricted in relation to the extent of movement of the valve member as the spool 94 moves out of the passage 74. The extent of movement of the valve member 75, and therefore the increase in restriction of flow through the passage 74, is a function of the return fuel line pressure.

When the fuel return system is blocked, the pressure in the fuel return rail increases to a level sufficient to move the valve member for restricting flow to the injectors. The valve member ultimately reaches a position in which the fuel return system pressure is stabilized as a result of the reduced quantity of fuel delivered to the injectors. That is to say, that the flow reduction to the injectors caused by movement of the valve member results in a related reduction in the pressure in the return rail. Hence, the pressure force on the valve member created by return rail pressure is stabilized due to movement of the valve member.

The valve member thereafter remains in a position to enable a requisite fuel flow to the injectors without overfueling the engine. In this manner, the flow of fuel to the injectors 32 is modulated to enable continued normal operation of the engine 11 at rated or reduced performance as desired and controlled by the configuration of valve member 75. This is so even though the return fuel system may be tampered with in such a way as to completely block the flow of excess fuel to the tank 12. Pressure-balancing surfaces at the ends of the spool 94 insure against fuel in the supply line exerting unbalanced pressure forces on the valve which would otherwise prevent modulation of the flow of supply fuel.

As shown in FIG. 2, the end 88 of the bore 80 and a chamber 98 (defined by the rear face of the piston 78 and the cylinder bore 82) are communicated by a pressure-equalizing passageway 100. The chamber 98 communicates with the inlet side of the pump 40 through a passage 102 which enables venting fuel and/or air which might otherwise be trapped in the valve and impede movement of the valve member.

Since movement of the valve member 75 is principally a function of the static pressure in the rail 61, the valve 44 continues to function even though the pressure reaction conduit 70 is tampered with but not completely closed off. That is to say, the only flow in the pressure reaction conduit 70 is that flow which is required to move the piston 78 and equalize the pressure in the chamber 96 and the rail 61'. Hence, the flow through the pressure reaction conduit 70 is relatively small and partially closing the conduit 70 merely reduces the responsiveness of the valve 44.

The new fuel governor is disabled by tampering only if the fuel return system is blocked and the valve 44 is disabled. Disabling the valve 44 cannot be accomplished unless the pressure passage 70 is completely blocked (as noted above), or the vent passage 102 is completely blocked. Blocking these additional lines is both difficult and easily discovered. Hence, the new fuel governor can be said to be substantially tamperproof.

In the valve 44 illustrated in FIG. 2, it is noted that the passage 74 is not completely closed by the valve member 75 since the diameter of the valve body 76 is smaller than the diameter of the passage 74; however, the valve 44 can be designed so that the valve member 75 completely closes off flow through the passage 74. It should be apparent, however, that since the valve member 75 moves according to the pressure in the return rail 61, the flow of fuel to the engine through the passage 74 is terminated only intermittently so that the engine ll continues to operate.

FIG. 3 shows another preferred fuel control 44 which functions substantially the same as the valve 44 of FIG. 2. The valve 44' is structurally similar to the valve 44 and parts of the valve 44', similar to previously described parts, are designated by corresponding primed reference characters.

The valve 44' includes a housing 73' defining a fuel fiow passage 74'. The passage 74 is formed by three separate intersecting drilled openings which enable a through flow of fuel from the discharge of fuel injection pump at one side of the housing 73' to the shutoff valve 46' on the opposite side.

A valve member 75 extends through the passage 74' and is movably supported in the housing to variably restrict flow of fuel through the passage. The valve member 75 is substantially the same as the valve member 75 described in reference to FIG. 2 except that the helical compression spring 86' is disposed in the chamber 98' and urges the rear face of the piston 78' toward the right as seen in FIG. 3.

The end closure 84' is defined by a platelike member which is bolted to the housing 73. The pressure reaction conduit 70 is coupled to the closure 84' for communication with the chamber 96 between the closure 84', piston 78 and the wall of the cylinder bore 82'. Suitable stops 92' extend from the plate 84' into the chamber 96' to limit movement of the valve member 75 toward the right.

The diameter of the valve member 75' is larger than the diameter of the flow passage 74 through which the valve member 75 extends and accordingly the valve member 75' is capable of completely terminating flow of fuel through the valve 74 when the valve member is in its extreme leftward position. Terminating fuel flow through the passage 74' generally will not occur since the valve 44 modulates the fuel flow as is described in reference to FIG. 2.

The end 88 of the bore 80 is defined by a suitable plug and the valve body 76' carries a stop 104 which engages the plug 88' to limit movement of the valve member 75' leftward. The space between the valve member 75' and the plug 88', and the chamber 98 surrounding the spring are suitably vented to enable unrestricted motion of the valve member 75'. The structure for venting these locations is not illustrated in FIG.

3, however, it may be similar to the passageway I00 and vent conduit 102 described in connection with FIG. 2.

Although the preferred embodiments of the present invention have been illustrated and described in considerable detail, the present invention should not be considered limited to the precise constructions shown. Various modifications, adaptations and uses of the disclosed system may occur to those skilled in the art, and it is the intention to cover all such adaptations, modifications and uses which come within the scope of the invention.

What is claimed is:

1. In a fuel injection system:

a. a fuel tank;

b. at least one fuel injector;

c. a fuel supply system for communicating fuel from said tank to said at least one injector at flow rates greater than the volume rate of injection of fuel into an engine by said. at least one fuel injector; said fuel supply system comprising a fuel pump;

. a fuel return system including an excess fuel manifold communicating with said injector and an excess fuel passage communicating said manifold with said fuel tank for returning excess fuel supplied to said injector to said tank;

. fuel flow control means between said fuel pump and said injector for modulating the flow of fuel to said injector in response to fuel pressure in said return passage to prevent injection of excessive amounts of fuel into an engine as a result of blockage of the fuel return system, said control means comprising:

a fuel flow control valve including a valve member movable for continuously variably restricting fuel flow to said injector in response to a pressure force applied to said valve member;

. a pressure-transmitting passage communicating fuel pressure in said excess fuel manifold to said valve member, said valve member moving to restrict fuel flow to said injector when the pressure force applied thereto by fuel pressure in said excess fuel manifold increases above a predetermined level; and,

. said valve member including pressure-balancing surfaces exposed to fuel in said supply system for preventing application of substantial unbalanced pressure forces on said valve member by fuel in said supply system.

2. The system claimed in claim 1 including a plurality of injectors, said injectors communicating with said fuel return manifold, said pressure-transmitting passage opening into said fuel return manifold.

3. The system claimed in claim 1 wherein said valve member includes a pressure reaction surface defining a movable wall of an expansible chamber, said pressure-transmitting passage opening into said chamber for maintaining the pressure in said chamber equal to the pressure in said fuel return manifold.

4. The system claimed in claim 1 wherein said valve member is movable between a first limit position enabling relatively unrestricted fuel flow to said injector and a second limit position providing for a maximum fuel flow restriction, and further including biasing means urging said valve member toward one of said positions.

5. The system claimed in claim 4 wherein said valve member includes a pressure reaction surface against which said pressure force acts, said surface oriented so that said pressure force acts in opposition to the biasing force of said spring means to move said valve member toward its second position.

6. The system claimed in claim I wherein the extent of movement of said valve member from a first position affording minimum restriction of fuel flow to said injector is a function of the fuel pressure in said fuel manifold, and said valve member moves to a position for restricting fuel flow to said injector at which the pressure in said manifold does not exceed a predetermined maximum level.

7. The system as claimed in claim 1 wherein said fuel flow control valve is integral with said fuel pump.

8. ln combination:

a. an internal combustion engine;

b. a fuel supply tank;

c. a fuel supply system between said tank and said engine including a fuel injection pump and a plurality of fuel injectors;

d. said pump normally supplying a volume rate of fuel flow to said fuel injectors which is in excess of the volume rate of injection of fuel into said engine to insure injection of adequately large fuel charges into said engine;

e. a fuel return system for returning excess fuel from said fuel injectors to said tank;

. fuel control means for modulating the flow of fuel to said injectors in response to fuel pressure in said fuel return system, said control means comprising:

i. a fuel-flow-controlling valve connected between said pump and said fuel injectors, said valve defined by a housing and a valve member movable in said housing, said valve member having a normal position enabling said pump to provide said normal fuel supply;

ii. said valve member including a pressure reaction surface forming a movable wall of an expansible chamber defined by said surface and said housing and opposed surfaces exposed to fuel flowing to said injectors whereby the pressure of fuel flowing to said injectors is substantially ineffective to move said valve member; and,

iii. a pressure-transmitting passage communicating fuel pressure in said fuel return system to said chamber, fuel pressure greater than a predetermined pressure in said fuel return system communicated to said chamber through said pressure-transmitting passage for applying a force to said reaction surface for moving said valve member from said normal position to variably restrict fuel flow to said injectors to maintain a predetermined limit between pump output pressure, and therefore fuel delivery, and return line pressure at any given engine speed and thereby enable continued substantially normal operation of the engine under load without oversupply of fuel.

9. In combination:

a. an internal combustion engine;

b. a fuel supply tank;

c. a fuel supply system between said tank and said engine including a fuel injection pump and a plurality of fuel injectors;

d. said pump normally supplying a volume rate of fuel flow to said fuel injectors which is in excess of the voiume rate of injection of fuel into said engine to insure injection of adequately large fuel charges into said engine;

e. an excess fuel manifold communicating with said injectors;

f. a fuel control valve for continuously varying the quantity of fuel supplied to said injectors by said pump in response to fuel pressure in said excess fuel manifold;

i. said valve including a valve member movable in relation to fuel pressure in said excess fuel manifold, said valve member moving from a position wherein fuel flow to said injectors is relatively unrestricted in response to increases in pressure in said excess fuel manifold;

ii. pressure-balancing surfaces on said valve member preventing application of substantial unbalanced pressure forces to said valve member by fuel in said fuel supply system; and,

iii. means cooperating with said valve member for creating a force acting on said valve member to tend to move said valve member to said position; and,

g. a static-pressure-transmitting conduit communicating the static fuel pressure from said excess fuel manifold to said valve member whereby said valve member moves from said position in response to increases in static pressure of fuel in said excess fuel manifold above a predetermined level to maintain a predetermined limit between pump output pressure, and therefore fuel delivery, and the pressure in said excess fuel manifold at any given engine speed and thereby enable continued substantially normal operation of said engine under load without oversupply of fuel. 

1. In a fuel injection system: a. a fuel tank; b. at least one fuel injector; c. a fuel supply system for communicating fuel from said tank to said at least one injector at flow rates greater than the volume rate of injection of fuel into an engine by said at least one fuel injector; d. said fuel supply system comprising a fuel pump; e. a fuel return system including an excess fuel manifold communicating with said injector and an excess fuel passage communicating said manifold with said fuel tank for returning excess fuel supplied to said injector to said tank; f. fuel flow control means between said fuel pump and said injector for modulating the flow of fuel to said injector in response to fuel pressure in said return passage to prevent injection of excessive amounts of fuel into an engine as a result of blockage of the fuel return system, saId control means comprising: g. a fuel flow control valve including a valve member movable for continuously variably restricting fuel flow to said injector in response to a pressure force applied to said valve member; h. a pressure-transmitting passage communicating fuel pressure in said excess fuel manifold to said valve member, said valve member moving to restrict fuel flow to said injector when the pressure force applied thereto by fuel pressure in said excess fuel manifold increases above a predetermined level; and, i. said valve member including pressure-balancing surfaces exposed to fuel in said supply system for preventing application of substantial unbalanced pressure forces on said valve member by fuel in said supply system.
 2. The system claimed in claim 1 including a plurality of injectors, said injectors communicating with said fuel return manifold, said pressure-transmitting passage opening into said fuel return manifold.
 3. The system claimed in claim 1 wherein said valve member includes a pressure reaction surface defining a movable wall of an expansible chamber, said pressure-transmitting passage opening into said chamber for maintaining the pressure in said chamber equal to the pressure in said fuel return manifold.
 4. The system claimed in claim 1 wherein said valve member is movable between a first limit position enabling relatively unrestricted fuel flow to said injector and a second limit position providing for a maximum fuel flow restriction, and further including biasing means urging said valve member toward one of said positions.
 5. The system claimed in claim 4 wherein said valve member includes a pressure reaction surface against which said pressure force acts, said surface oriented so that said pressure force acts in opposition to the biasing force of said spring means to move said valve member toward its second position.
 6. The system claimed in claim 1 wherein the extent of movement of said valve member from a first position affording minimum restriction of fuel flow to said injector is a function of the fuel pressure in said fuel manifold, and said valve member moves to a position for restricting fuel flow to said injector at which the pressure in said manifold does not exceed a predetermined maximum level.
 7. The system as claimed in claim 1 wherein said fuel flow control valve is integral with said fuel pump.
 8. In combination: a. an internal combustion engine; b. a fuel supply tank; c. a fuel supply system between said tank and said engine including a fuel injection pump and a plurality of fuel injectors; d. said pump normally supplying a volume rate of fuel flow to said fuel injectors which is in excess of the volume rate of injection of fuel into said engine to insure injection of adequately large fuel charges into said engine; e. a fuel return system for returning excess fuel from said fuel injectors to said tank; f. fuel control means for modulating the flow of fuel to said injectors in response to fuel pressure in said fuel return system, said control means comprising: i. a fuel-flow-controlling valve connected between said pump and said fuel injectors, said valve defined by a housing and a valve member movable in said housing, said valve member having a normal position enabling said pump to provide said normal fuel supply; ii. said valve member including a pressure reaction surface forming a movable wall of an expansible chamber defined by said surface and said housing and opposed surfaces exposed to fuel flowing to said injectors whereby the pressure of fuel flowing to said injectors is substantially ineffective to move said valve member; and, iii. a pressure-transmitting passage communicating fuel pressure in said fuel return system to said chamber, fuel pressure greater than a predetermined pressure in said fuel return system communicated to said chamber through said pressure-transmitting passage for applying a force to said reaction surface for moving said valve member from said normal position to variably restrict fuel flow to said injectors to maintain a predetermined limit between pump output pressure, and therefore fuel delivery, and return line pressure at any given engine speed and thereby enable continued substantially normal operation of the engine under load without oversupply of fuel.
 9. In combination: a. an internal combustion engine; b. a fuel supply tank; c. a fuel supply system between said tank and said engine including a fuel injection pump and a plurality of fuel injectors; d. said pump normally supplying a volume rate of fuel flow to said fuel injectors which is in excess of the volume rate of injection of fuel into said engine to insure injection of adequately large fuel charges into said engine; e. an excess fuel manifold communicating with said injectors; f. a fuel control valve for continuously varying the quantity of fuel supplied to said injectors by said pump in response to fuel pressure in said excess fuel manifold; i. said valve including a valve member movable in relation to fuel pressure in said excess fuel manifold, said valve member moving from a position wherein fuel flow to said injectors is relatively unrestricted in response to increases in pressure in said excess fuel manifold; ii. pressure-balancing surfaces on said valve member preventing application of substantial unbalanced pressure forces to said valve member by fuel in said fuel supply system; and, iii. means cooperating with said valve member for creating a force acting on said valve member to tend to move said valve member to said position; and, g. a static-pressure-transmitting conduit communicating the static fuel pressure from said excess fuel manifold to said valve member whereby said valve member moves from said position in response to increases in static pressure of fuel in said excess fuel manifold above a predetermined level to maintain a predetermined limit between pump output pressure, and therefore fuel delivery, and the pressure in said excess fuel manifold at any given engine speed and thereby enable continued substantially normal operation of said engine under load without oversupply of fuel. 